Induction system and method of operating an engine

Abstract: An induction system and control method for an internal combustion engine that will improve running under low speed, low load conditions by increasing turbulence in the combustion chamber through the use of a control valve (61) positioned in the induction system (38) for the engine. Under high speed, high load conditions, the control valve is held in an open position and thus, the engine is capable of obtaining high output since there is no restriction to the intake air flow. In addition, transient conditions of the engine, such as variations in idle speed, variations in the amount of EGR, changes in speed, such as acceleration or deceleration, starting and warmup, are compensated for by positioning the throttle control valve to obtain optimum performance, and in some instances, the amount of fuel supplied to the engine is also varied so as to improve exhaust emission control and reduce fuel consumption.

Description: BACKGROUND OF THE INVENTION This invention relates to an induction system for an internal combustion engine and to a method of operating an engine and more particularly to an induction system and method of operating an engine to improve performance under certain types of transient conditions. As is well known, the induction system for an internal combustion engine is particularly important in determining the performance of the engine. Induction systems in conventional engines generally represent a compromise between the free-breathing type of induction systems that provide high performance by introducing the charge into the combustion chamber in an unrestricted fashion and without introducing turbulence to the inducted air charge and the low speed or mid-range type of induction system that provides a higher flow velocity and turbulence in the combustion chamber. The free breathing system, although it permits maximum charging and high performance, will provide less than desirable performance under low speed, low load conditions. An induction system that provides good performance under low load conditions, however, will not offer the ability to induct sufficient air so as to achieve maximum performance. Therefore, it has been the practice with conventional engines to compromise the induction system between these two extremes. There have also been provided induction systems that include devices for introducing turbulence and/or high velocity to the intake charge under some running conditions and substantially unrestricted induction under high speed high load conditions. One such system is described in the co-pending application of Yoshiharo Isaka entitled "Tumble Control Valve for Intake Port," Serial No. 07/834,604, filed February 12, 1992, and assigned to the assignee hereof. This system, shows a number of embodiments of induction systems wherein there is provided a control valve in the intake passage which is moveable between a first, opened position in which unrestricted charging is provided and wherein the charge flows into the combustion chamber in a generally axial direction for high speed running. Under low speed or mid-range performance, the control valve is moved to another position wherein the charge which enters the combustion chamber is redirected so as to increase the turbulence in the combustion chamber and also the velocity at which the charge is inducted. The turbulence is generated by introducing either a tumble and/or a swirl to the intake charge. Tumble is generally referred to as a type of swirl that occurs about an axis that extends transversely to the axis of the cylinder bore. Swirl, on the other hand, is the type of motion in which rotation occurs about an axis that is coincident with or parallel to the cylinder bore axis. In the systems shown in that application, the position of the control valve is set in response to certain engine running parameters, normally speed and/or load. This system is extremely effective in proviing good performance throughout the entire engine speed and load ranges. Moreover, to improve combustion to enlarge the lean limitation range, by providing a movable swirl generating deflecting plate in an intake port so that the deflector plate is controlled to increase the swirl ratio of transient operation, there is provided a movable swirl generating deflector plate in an intake port, and is controlled in accordance with the operating condition of an engine, in association with the negative pressure adjustment of an actuator by a solenoid valve which is controlled to be energised and de-energised by means of a control unit. In accordance with the throttle valve opening degree and the engine rotational speed, the deflector plate as lowered upon low load operation of an engine to increase the swirl ratio, while the deflector plate is raised upon high load operation to increase the swirl ratio. Further, the deflector plate is lowered to increase the swirl ratio upon accelerating operation in which the throttle valve opening degree changing ratio at the throttle sensor becomes larger, thereby it is possible to carry out optimum combustion. However, in JP61160520 the deflector plate is lowered upon low load operation to increase the swirl ratio while upon high load operation the deflector plate is raised to increase the swirl ratio as well. For example, irrespective of the load conditions, but controlled in response thereto, it is an aim cf said solution to increase the swirl ratio to provide better combustion conditions. Moreover, EP-A-0 221 312 provides an electronically controlled fuel supply system having a simplified intake system including idle control means for generating an idle control while under low load conditions said idle control means controls an auxiliary intake passage for introducing a swirl motion in addition to the main charge supply. However, there is another type of condition wherein modification of the amount or direction of swirl and/or tumble may be desirable. This other type of condition is a transient condition wherein the engine is not operating at a steady state condition but rather is changing its state. Examples of such transient conditions are during idle when attempts are made to stabilize idle speed, when emission control is being practiced by attempting to run on a lean mixture and to reduce nitrous oxide emissions through the use of exhaust gas recirculation (EGR) or on starting and/or cold warmup. Under these conditions, variations in the steady state position of the control valve can significantly improve performance and reduce the emission of unwanted hydrocarbons and other constituents in the exhaust gases. It is, therefore, a principal object of this invention to provide an improved induction system and induction method for an internal combustion engine for controlling the idle speed of an engine to maintain idle speed stability. According to the present invention this objective is solved for a device by an induction system for an internal combustion engine having a pair of relatively movable components defining a combustion chamber which varies cyclically in volume upon the relative movement between said components, an induction system for delivering an intake charge to said combustion chamber, control valve means in said induction system and movable between a first opened position wherein the flow of charge from said induction system to said combustion chamber enters said combustion chamber without generating significant turbulence and at a relatively lower velocity and a closed position wherein the charge entering the combustion chamber is turbulent and at a high velocity, engine sensing means for sensing at least one running condition of said engine, means for sensing a transient condition wherein the transient running condition is a deviation from a target idle speed, and control means for setting the position of said control valve in response to the sensed engine condition and the sensed transient condition. Further, according to the present invention this objective is solved by an operating method for an intemal combustion engine having a pair of relatively movable components defining a combustion chamber which varies cyclicly in volume upon the relative movement between said components, an induction system for delivering an intake charge to said combustion chamber, control valve means in said induction system and movable between a first opened position wherein the flow of charge from said induction system to said combustion chamber enters said combustion chamber without generating significant turbulence and at a relatively low velocity and a closed position wherein the charge entering the combustion chamber is turbulent and at a high velocity, said method comprising the steps of sensing at least one running condition of said engine, sensing a transient condition, and setting the position of said control valve in response to the sensed engine condition and the sensed transient condition wherein the transient running condition is a deviation from the target idle speed. The features of the invention are adapted to be embodied in an internal combustion engine having a pair of relatively moveable components which define a combustion chamber whose volume varies cyclically upon the relative movement of the components. An induction system is provided for introducing and charge to the combustion chamber. The induction system includes control valve means moveable between a first position wherein the charge introduced to the combustion chamber flows into the combustion chamber in nonturbulent, substantially unrestricted condition and a second position wherein the charge enters the combustion chamber at a restricted, higher velocity and turbulent condition. In addition to these features, means are provided for sensing at least one engine running condition and at least one transient condition. In accordance with an apparatus for embodying one of these features of the invention, means control the position of the control valve in response to both the sensed engine running condition and the transient condition, when it is existent. In accordance with a method for practicing this feature of the invention, the control valve is positioned in response to the sensed running condition and the sensed transient condition, if it is existent. In connection with these features of the invention, the transient condition is the idle speed. In accordance with an apparatus for performing these features of the invention, the control valve is positioned in response to the sensed transient condition by a control means. In accordance with a method for performing these features of the invention, the control valve is positioned in response to the sensed existence of the transient condition. With respect to these features of the invention, the sensed transient condition is the idle speed. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a partial cross-sectional view taken through a single cylinder of an internal combustion engine constructed and operated in accordance with certain embodiments of the invention, with portions of the system shown schematically. Figure 2 is a view, in part similar to Figure 1, and shows further details or the control system and for correcting the amounts of fuel injected in response to certain transient conditions. Figure 3 is a graphical view showing how the idling speed can be stabilized in accordance with a first embodiment of the invention and depicts the engine speed in RPM in relation to time and also the position of the induction system control valve in order to stabilize idle speed. Figure 4 is a graphical view showing the target idle speed in response to engine operating temperature. Figure 5 is a block diagram showing the control routine for maintaining target idle speed by employing the induction system control valve in accordance with this first embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION Referring now in detail to the drawings and initially to Figure 1, an internal combustion engine constructed and operated in accordance with several embodiments of the invention is shown partially and in cross section and is identified generally by the reference numeral 31. Since the invention is directed primarily to the induction system for the engine 31 and the method of inducting the charge into the engine, only the upper portion of a single cylinder of the engine has been depicted. It should be readily apparent to those skilled in the art how the invention may be practiced in conjunction with engines of varying cylinder numbers and cylinder configurations. In addition and as will become readily apparent to those skilled in the art, the invention may be also practiced in conjunction with nonreciprocating-type of engines such as rotary engines of any known type. The engine 31 includes a cylinder block 32 that is formed with a cylinder bore 33 in which a piston 34 reciprocates in a known manner. The piston 34 is connected by means of a connecting rod 35 to a crankshaft (not shown), which is rotatably journalled in a crankcase chamber in a well-known manner so as to provide output power from the engine 31. A cylinder head 36 is affixed in any known manner to the cylinder block 32 and is formed with a recess 37, which cooperates with the cylinder bore 33 and the head of the piston 34 so as to form the variable volume combustion chamber of the engine 31. An induction system, indicated generally by the reference numeral 38, is provided for introducing a charge to this combustion chamber. This induction system includes an air inlet 39 in which a flow controlling throttle valve 41 is positioned. The throttle valve 41 is controlled in any known manner by an operator so as to set the running speed for the engine 31. Air is inducted to the air inlet 39 from a suitable air inlet device (not shown), which may include an air silencer and an air filter. The air from the air inlet device 39 is delivered to a plenum chamber 42 of an intake manifold, indicated generally by the reference numeral 43. This intake manifold 43 has a plurality cf runners 44, each of which serves an induction passage 45 formed in the intake side of the cylinder head 36 and which terminates at a valve seat 46. An intake valve 47 is supported for reciprocation within the cylinder head 36 in a known manner and is operated from an intake cam shaft 48 by means of a thimble-type tappet 49 that is supported for reciprocation within the cylinder head 36 in a known manner and which is associated with the stem of the intake valve 47. There is also provided a return spring assembly 51 for urging the intake valves 47 to their closed position, as is well known in this art. The intake cam shaft 48 is driven at one-half crankshaft speed by any type of drive mechanism. An exhaust passage 52 is formed in the side of the cylinder head 36 opposite the intake passage 45 and extends from a valve seat 53 in the cylinder head 36, which communicates with the combustion chamber 37 to an exhaust manifold 54 that discharges the exhaust gases to the atmosphere through any suitable exhaust system (not shown). An exhaust valve 55 is supported for reciprocation within the cylinder head 36 in a known manner and is opened by an exhaust cam shaft 56, which is suitably journalled in the cylinder head 36 and which operates the exhaust valve 56 through a thimble tappet 49, which is also slidably supported in the cylinder head assembly 36 in a known manner. A valve spring 51 urges the exhaust valve 55 to its closed position. A fuel injector 57 is supported in the cylinder head 36 in a known manner and injects fuel into the intake passage 45. In the illustrated embodiment, the fuel injector 57 is of the electrically operated type and is opened and closed by an electronic control unit (ECU), indicated generally by the reference numeral 58 and shown schematically in this figure, with further details of its components being shown in Figure 2, which will be referred to subsequently. The ECU 58 receives signals from a number of sensors indicative of engine conditions such as engine speed a , engine temperature (coolant temperature) b , and other conditions in order to practice certain embodiments of the invention, as will be described. Any known type of control routine may be employed for controlling the normal engine operating condition of the fuel injector 57, and this may include various other types of known sensors such as sensors that determine intake air volume and/or temperature, as indicated at b , which may also be determined by a throttle position sensor. The valve mechanism as thus far described, including the intake and exhaust cam shafts 48 and 56, is enclosed by a cam cover 59 that is affixed to the cylinder head 36 in any known manner. The construction of the engine 31 as thus far described may be considered to be conventional and, for that reason, any details of the engine construction which are not illustrated may be of any type well known in the art. In accordance with the invention, the induction system as thus far described, including the intake passages 45, is configured so that the charge that enters the combustion chamber 37 will be substantially unrestricted and will flow in a generally axial direction so as to not generate any turbulence in the combustion chamber. As is well known, this provides very effective and efficient charging efficiency, but will not provide optimum running under low engine speeds and load. Therefore, and in accordance with the invention, a control valve, indicated generally by the reference numeral 61, is provided in the induction system 43 for generating turbulence in the combustion chambers 37 and restricting the flow through the induction system 43 to increase the flow velocity under certain running conditions. This control valve 61 is mounted in a transversely extending bore 62 formed in the cylinder head 36 and includes a valving portion 63 that is provided with a cutout 64 so as to redirect the flow into the combustion chamber when in its closed positions, including the fully closed position as shown in Figure 1. The construction of the control valve 61 may be of any of the types disclosed in the aforenoted copending application, Serial No. 07/834,604, the disclosure of which is incorporated herein by reference. The control valve 61 in its closed position may generate either tumble, swirl, or a combination of both, depending upon which type of construction from the aforenoted application is employed. Said another way, the control strategies, which will be described herein, can be employed with any of the types of control valves shown in the aforenoted copending application and any other type of control valve that is designed so as to provide turbulence and increase in velocity of induction charge under some running conditions and substantially unrestricted flow under other running conditions. The position of the control valve 61 is controlled by a servo motor (not shown) and which receives a control signal A from the ECU 58 in conjunction with control strategies of the type that will be described. In addition, a position sensor outputs a signal c back to the ECU 58 so as the ECU 58 can monitor the actual position of the control valve 61 for the control routines that will be employed. Referring now to Figure 2, this shows in more detail the components of the ECU 58 and their interrelationship to the control valve 61 and the fuel injector 57. The ECU 58, as has been noted, receives certain signals from engine condition sensors, and these sensors are indicated as a block at 65 and may include sensors that sense engine speed, throttle valve position or load, etc. The ECU 58 has an injection control block 66 that provides the control signal B to the fuel injector 57 for controlling not only the initiation but also the timing of fuel injection. In addition, there is a control valve control block 67 that outputs the signal A to the intake control valve 61 for controlling its position. The signal c, indicative of the position of the control valve 61, is provided by a position sensor, indicated schematically at 68 in Figure 2. In addition, and in accordance with certain embodiments of the invention, the amount of fuel injected from the normal requirements for given running conditions may be adjusted by a correction section 69, which can correct for certain conditions, as will be hereinafter noted. It is to be understood that the basic control routine for controlling the position of the control valve 61 and the amount and duration of fuel injected by the fuel injector 57 may be varied by any known control routine. Those of the control valve 61 may be as set forth in the aforenoted copending application, Serial No. 07/834,604. This invention deals with the accommodation of a certain transient condition and the control of the engine in response to this transient condition which is the maintenance of the desired target idle speed. As is well known, various conditions can cause the idle speed of the engine to vary. Conventionally, the idle speed may be stabilized by adjusting things such as spark timing and/or throttle valve position or bypass air flow around the throttle valve so as to maintain a stabilized idle speed. In accordance with a feature of this invention, the idle speed can be stabilized by changing the position of the control valve 61. The reason idle speed can be maintained by adjusting the position of the control valve 61 is that the control valve 61 varies the degree of turbulence created in the combustion chamber, depending upon its position. That is, the further the degree of movement of the control valve 61 toward its fully closed position, as shown in Figure 1, will determine the amount of turbulence induced. As the turbulence increases, flame propagation in the combustion chamber 37 will increase. Therefore, all other factors being held ecual and considered normal, it is possible to increase the idle speed of the engine by closing the control valve and decreasing the idle speed by opening of the control valve. Figure 3 shows how this can be accomplished, with the top view showing the variation of engine idle speed from target speed in response to time and the lower curve showing the position of the control valve 61 in response to the sensed engine speed so as to maintain the desired idle speed. Figure 4 is a graphical view showing the target idle speed in relation to engine temperature. The target idle speed is maintained higher when the engine is cold and is reduced to normal idle speed as the engine reaches its operating temperature. Referring now specifically to Figure 3, at point X the target idle speed is maintained; but as the time increases, the actual speed of the engine may increase above target idle speed due to varying factors. In order to reduce the speed, the control valve 61 is rotated from a partially closed position, as shown in Figure 1, which is the normal idle position under most control routines, toward an open position so as to reduce turbulence, which, as aforenoted, may be either tumble, swirl, or a combination of them. This opening continues until the engine speed returns to the target idle speed. At this time the control valve 61 will then be returned to the normal idle speed setting. If, however, during the time period a the idle speed then decreases from the target idle speed, the control valve is moved from the idle position toward a more fully closed position so as to increase the tumble action and turbulence, and accordingly increase the speed of the engine. This occurs until the time a has elapsed and target speed is again reached. The time period b shows an increase in target idle speed due to variables and the return back to the target idle speed by again opening the control valve 61 from the idle position so as to decrease turbulence and reduce engine speed. Figure 5 is a block diagram showing the control routine or the ECU 58 so as to achieve the aforenoted result. This program is a subroutine of any conventional control routine for controlling the position of the control valve 61, as aforenoted. Referring to Figure 5, when the subroutine starts, the program moves to the step S1 so as to read the engine conditions, including engine temperature and actual engine speed. The program then moves to the step S2 so as to determine if an idle switch (which may be the throttle position switch) indicates that the throttle valve 41 is in its idle position. If it is not, the program moves to the normal control routine. If, however, it is determined at the step S2 that the idle switch indicates that the throttle valve 41 is in its idle position (again, this can be determined merely by the throttle position sensor), the program moves to the step S3. At the step S3, the desired engine idle speed or target engine idle speed is determined in response to engine operating temperature from the curve of Figure 4. The program then moves to the step S4 to compare the actual engine speed with the target idle speed. A determination is made at the step S4 to determine if the actual speed is lower than the target idle speed. If, at the step S4, it is determined that the actual idle speed is not lower than the target idle speed, then the program moves to the step S5 so as to cause the control valve 61 to be rotated toward its open position and reduce the turbulence. The program then repeats back to the step S1. If, however, at the step S4 it has been determined that the actual engine speed is lower than the desired engine speed, then it is necessary to increase the turbulence in the combustion chamber by closing the control valve 61 from its present position, and this is done at the step S6.

Claims: An induction system for an internal combustion engine having a pair of relatively movable components defining a combustion chamber which varies cyclically in volume upon the relative movement between said components, an induction system for delivering an intake charge to said combustion chamber, control valve means in said induction system and movable between a first opened position wherein the flow of charge from said induction system to said combustion chamber enters said combustion chamber without generating significant turbulence and at a relatively lower velocity and a closed position wherein the charge entering the combustion chamber is turbulent and at a high velocity, engine sensing means for sensing at least one running condition of said engine, means for sensing a transient condition wherein the transient running condition is a deviation from a target idle speed, and control means for setting the position of said control valve in response to the sensed engine condition and the sensed transient condition. The induction system of claim 1, further including charge forming means for supplying fuel to the engine and means for controlling the amount of fuel supplied by the charge forming means in response to the sensed engine conditions. The induction system of claim 1, wherein the engine comprises a reciprocating engine and one of the relatively movable components comprises a cylinder block cylinder head assembly and the other of the relatively movable components comprises a piston slidably supported within a cylinder bore in the cylinder block . An operating method for an internal combustion engine having a pair of relatively movable components defining a combustion chamber which varies cyclicly in volume upon the relative movement between said components, an induction system for delivering an intake charge to said combustion chamber, control valve means in said induction system and movable between a first opened position wherein the flow of charge from said induction system to said combustion chamber enters said combustion chamber without generating significant turbulence and at a relatively low velocity and a closed position wherein the charge entering the combustion chamber is turbulent and at a high velocity, said method comprising the steps of sensing at least one running condition of said engine, sensing a transient condition, and setting the position of said control valve in response to the sensed engine condition and the sensed transient condition wherein the transient running condition is a deviation from the target idle speed.

Inventors: TADA ATSUSHI, TADA, ATSUSHI
Applicants: YAMAHA MOTOR CO LTD, YAMAHA HATSUDOKI KABUSHIKI KAISHA
Application year: 1994
Main classification: F02B31
IPC codes: F02B31